how to use zebra_scanner_plugin for flutter application (android)

Question

I'm using zebra_scanner_plugin for rfid scan for my android application. I have followed this link instruction https://pub.dev/packages/zebra_scanner_plugin (how to use section). After doing everything. I tried to use the method

Future<void> initAndConnectScanner() async {
  try {
    await ZebraScannerPlugin.initScanner;
    await ZebraScannerPlugin.connect();
  } catch (e) {
    print("Error initializing or connecting: $e");
  }
}

**but once I click button to invoke this , I'm getting below error and application is crashing. I' doing something wrong ? Do I need to write java code as well ?

Failed to handle method call
E/MethodChannel#zebra_scanner_plugin(18987): java.lang.NullPointerException: Attempt to invoke virtual method 'com.zebra.scannercontrol.DCSSDKDefs$DCSSDK_RESULT com.zebra.scannercontrol.SDKHandler.dcssdkSetDelegate(com.zebra.scannercontrol.IDcsSdkApiDelegate)' on a null object reference
E/MethodChannel#zebra_scanner_plugin(18987):    at com.androsys.zebra_scanner_plugin.ZebraScannerEngine.initialize(ZebraScannerEngine.java:52)
E/MethodChannel#zebra_scanner_plugin(18987):    at com.androsys.zebra_scanner_plugin.ZebraScannerEngine.<init>(ZebraScannerEngine.java:31)
E/MethodChannel#zebra_scanner_plugin(18987):    at com.androsys.zebra_scanner_plugin.ZebraScannerEngine.getInstance(ZebraScannerEngine.java:37)